Warm mix asphalt production system and method

ABSTRACT

A warm mix asphalt plant comprising a counter-flow drum, apparatus for precisely metering flows of A/C and water, an asphalt expander with no moving internal parts where a circular curtain of flowing clean water is mixed with a coaxial circular curtain of moving heated A/C to create asphalt foam which is heated and mixed inside a lower portion of the asphalt expander and then distributed to cover aggregate inside the counter-flow drum.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of a provisional application filedon Feb. 18, 2008, and having Ser. No. 61/029,515. This application alsoclaims the benefit of a utility application filed on Feb. 17, 2009, andhaving Ser. No. 12/372,471.

BACKGROUND OF THE INVENTION

This invention relates to a counter-flow asphalt plant used to produce avariety of asphalt compositions. However, the present invention could beapplicable to non-counter-flow plants as well. More specifically, thisinvention relates to kits to retrofit, as well as newly constructedcounter-flow (and non-counter-flow) asphalt plants with a warm mixasphalt capability.

Several techniques and numerous equipment arrangements for thepreparation of warm asphaltic mix, also referred to by the trade as“warm mix” or “WMA”, are known from the prior art. Particularly relevantto the present invention is the use of chemical additives to the normalbitumen binder and the use of complex WMA systems with numerous movingparts, as well as plants which are difficult to retro-fit into existingasphalt plants.

SUMMARY OF THE INVENTION

More specifically, an object of the invention is to provide a WMAcounter-flow asphalt plant kit capable of transforming an existing hotmix asphalt (HMA) plant into a dual-mode (HMA and WMA) asphalt plant.

Another object of the invention is to provide a WMA asphalt plant kitwhich is relatively easily installed into existing HMA plants.

It is a feature of the present invention to use an asphalt expanderwhich includes no internal moving parts and may utilize just clean waterto expand the bitumen binder.

The present invention includes the above-described features and achievesthe aforementioned objects.

Accordingly, the present invention comprises newly constructed plants,as well as a kit for retrofitting WMA capabilities into a pre-existingHMA counter-flow asphalt plant which include an asphalt expander, withno moving internal parts, an internal expanded asphalt injection pipeassembly, sources of water and asphalt cement, and interconnectingstructure.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following description of the drawings, in which like referencenumerals are employed to indicate like parts in the various views:

FIG. 1 is a simplified cross-sectional view of a counter-flow asphaltplant which includes therein and coupled thereto a WMA kit of thepresent invention.

FIG. 2 is a cross-sectional view of the asphalt expander of the presentinvention where dotted lines with arrows refer to water flow paths anddashed lines with arrows refer to A/C flow paths.

FIG. 3 is a plan view of a water source package of the presentinvention.

FIG. 4 is a perspective view of a flow diverter from inside of theasphalt expander of FIG. 2.

FIG. 5 is a cross-sectional view of the water source package taken online A-A of FIG. 3.

FIG. 6 is a perspective view of the expanded asphalt injection pipeassembly of the present invention.

FIG. 7 is a close-up view of an end of the expanded asphalt injectionpipe assembly of FIG. 6.

FIG. 8 is a top view of the expanded asphalt injection pipe assembly ofFIGS. 6 and 7 where the dashed lines represent internal structure hiddenfrom view.

FIG. 9 is a side view of the expanded asphalt injection pipe assembly ofFIGS. 6, 7 and 8 where the dashed lines represent internal structurehidden from view.

FIG. 10 is a cross-sectional view of the expanded asphalt injection pipeassembly taken on line A-A of FIG. 9.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to the drawings, where like numerals refer to like matterthroughout, and referring in greater detail, attention is first directedto a prior art counter-flow asphalt plant as shown in the illustrationof FIG. 1 except that it is shown with the kit of the present inventioncoupled thereto. The prior art asphalt plant of FIG. 1 is similar to oneshown and described in greater detail in Hawkins U.S. Pat. No. 4,787,938incorporated herein by reference.

The augmented HMA plus WMA asphalt plant 1000 of the present inventionis shown with a counter-flow HMA asphalt plant rotating drum 100 with anaggregate entrance end 102 and asphalt exit end 104 which typicallycontains an asphalt cement internal drum delivery pipe 600 or the like.Also shown is “expanded asphalt” injection pipe assembly 700 of thepresent invention, as well as the structure coupled thereto to feed itwith expanded asphalt foam. Shown is a water pumping and metering skid300 (FIGS. 3 and 5) which provides water past a check valve 350 to theasphalt expander 200 to be used in the WMA asphalt foam productionprocess, as well as an asphalt package skid 400 which is a prior artpackage which provides a controlled administration of asphalt cement(A/C), which may be a bitumen binder. Water pumping and metering skid300 is coupled to a 3-way asphalt cement valve 500 which alternatelyprovides A/C to asphalt cement internal drum delivery pipe 600 orasphalt cement check valve 800 and then on to asphalt expander 200 withan asphalt expander material input top end 202 and an asphalt expandermaterial output bottom end 204 which couples with a portion of expandedasphalt injection pipe assembly 700. Central controls 900 can beelectric, manual or omitted. Central controls 900 may providemicroprocessor control of the flow rates and duration of water, A/C andvalve switching, etc.

It should be understood that it also possible to eliminate the originaldrum asphalt cement internal drum delivery pipe 600 and the 3-wayasphalt cement valve 500 and use the expanded asphalt injection pipeassembly 700 for both HMA applications with non-foamed asphalt cementand WMA applications with foamed asphalt cement.

In operation, the system of the present invention functions as follows:counter-flow HMA asphalt plant rotating drum 100 is retro-fitted with anexpanded asphalt injection pipe assembly 700 which is supplied withexpanded asphalt foam via an asphalt expander 200 which is suppliedasphalt by asphalt package skid 400 and water by water pumping andmetering skid 300. As heated aggregate passes the burner, expandedasphalt foam is forced from the self-draining expanded asphalt foaminjection nozzles 704 to coat the aggregate with expanded asphalt foam.

The present invention can be better understood by now referring to FIG.2, which shows an asphalt expander material input top end 202 which isconfigured to receive therein and therethrough heated A/C. Asphaltexpander material input top end 202 is preferably made of stainlesssteel, but other suitable substitute materials could be used as well. Inone embodiment, asphalt expander 200 can have a layer of insulation tohelp maintain internal temperature and to help prevent clogging, etc.A/C is pumped through asphalt expander material input top end 202 viacoupling with a prior art asphalt package skid 400 (FIG. 1). The A/Ccontacts omni-directional flow diverter 206, which forces the A/C tomove away from the edges of asphalt expander 200. Asphalt expander 200is shown having an asphalt expander material output bottom end 204 withits four-tabbed base plate 232 and an asphalt expander interior centralsupport shaft 221 disposed therebetween along a longitudinal asphaltexpander axis 203.

Also shown is double-side wall pipe 208, which is shown having a waterinlet port 210 extending therethrough. Double-side wall pipe 208comprises double-walled pipe exterior wall 212 and double-walled pipeinterior wall 213, which creates double-walled pipe interior hot oilvoid 214. Water inlet port 210 provides a point where water is meteredinto internal water port 216 via the water pumping and metering skid300. The water exiting the internal water port 216 (water flow pathsshown as dotted line) contacts the flowing heated A/C (A/C flow path isshown as a dashed line) and preferably creates an A/C foam with theconsistency similar to that of shaving cream which moves through theasphalt expander 200 and mixes as it contacts various objects therein,such as first expansion flow diverter 222, second expansion flowdiverter 224, third expansion flow diverter 226, fourth expansion flowdiverter 228 and central flow diverter 230. The asphalt expander 200 isheated via pumping heat out into heated oil entry port 220 through thedouble-walled pipe interior hot oil void 214 and out of heated oil exitport 218.

Now referring to FIG. 3, there is shown the water pumping and meteringskid 300 which includes a water pumping and metering base skid 31 whichprovides support for all of the structure thereon. Also shown iselectric motor 32 which could be a 5 HP TEFEC 1800 RPM 3-phase 460 voltelectric motor, with a variable frequency drive module, or a suitablesubstitute which is coupled directly to or drives via a sheave and belt,or the like, the water pump 33, which could be a 3-section/piston rotarypositive displacement water pump. Water is provided to the water pump 33via water inlet location 35 and water filter 34. Water pump 33 pumps thewater to water meter 36, which may be a Sparling FM656 water meter whichrequires 110V AC power. Water meter 36 provides water to a 4-way couplerwhich is coupled to water pressure relief valve 37, which has a reliefvalve output 38, which can return water to a tank (not shown). A 4-waycoupler is also coupled to water on/off valve 39, which could be a 110VAC solenoid valve which goes to OFF without power and a water pressuregauge (0-200 psi) 43 and shutoff valve 430. Water on/off valve 39 iscoupled to water skid output 40 via 3-way manual or electric valve 41,which also has a calibration water output 42.

The narrow lines connecting the various components are optionalelectronic control lines for linking water source controls 903 and thento central controls 900 (FIG. 1) via line 309.

The water pumping and metering skid 300 provides a closely controlledsupply of clean cold water to the asphalt expander 200. The amount ofwater is approximately between 1-4% of the mass weight of the A/Cbinder.

Assuming a 400-tons per hour asphalt production rate with a 5% A/C(i.e., 5% of the 400 tons per hour output is A/C) with a 3% of the A/Cweight being water, you would need approximately 2.4 gallons of waterper minute. Depending upon how much water (1-4%) is added to the A/C,the A/C can expand between 3-18 times.

Now referring to FIG. 1, there is shown an asphalt package skid 400. Itshould be understood that the asphalt package is a common component ofevery HMA counter-flow drum asphalt plant. It will vary in some detailsfrom plant to plant; however, it should be understood that in general,the asphalt package skid 400 meters the A/C to be provided to the drum.The same system can be used and adjusted to meter the A/C for WMAapplications as for HMA applications. Optional A/C controls may becoupled to central controls 900 via line 409.

Now referring to FIG. 4, there is shown the internal components ofasphalt expander 200, which includes an asphalt expander interiorcentral support shaft 221 with an omni-directional flow diverter 206disposed on its top end. Also disposed on asphalt expander interiorcentral support shaft 221 is first expansion flow diverter 222, secondexpansion flow diverter 224, third expansion flow diverter 226, fourthexpansion flow diverter 228 and central flow diverter 230. It shouldalso be understood that there could be fewer or more than 4 diverterstages. At the bottom end of asphalt expander interior central supportshaft 221, there is shown four-tabbed base plate 232. The expanded A/Cis mixed by moving around the various expansion flow diverters 222, 224,226, 228 and 230.

Now referring to FIG. 5, there is shown a cross-sectional view of thewater pumping and metering skid 300 taken on line A-A of FIG. 3. It isshown having a superstructure with lifting point 301 such that the waterpumping and metering skid 300 is configured to be lifted from above viaa crane or other lifting machine. Also shown is control line 509.

Now referring to FIG. 6, there is shown an expanded asphalt injectionpipe assembly 700 with an expanded asphalt injection pipe distal end702, an expanded asphalt injection pipe material inlet end 708, and anexpanded asphalt injection pipe inspection port end 706.

Now referring to FIG. 7, there is shown a close-up of the expandedasphalt injection pipe distal end 702 with a plurality of expandedasphalt injection pipe spray nozzles 704 and the expanded asphaltinjection pipe nozzle opening flanges 750.

Now referring to FIG. 8, there is shown a top view of the expandedasphalt injection pipe assembly 700 of FIGS. 6 and 7. The dotted linesinside the expanded asphalt injection pipe assembly 700 show thelocation of internal pipes and pipe walls. Lines 720 are heated oillines for providing a path for hot oil to be pumped so as to provideheating capabilities to keep the expanded asphalt foam flowing freely.

Now referring to FIG. 9, there is shown a side view of the expandedasphalt injection pipe assembly 700 of FIGS. 6-8, where the dotted linesrefer to internal pipes and pipe walls.

Now referring to FIG. 10, there is shown a cross-sectional view of theexpanded asphalt injection pipe assembly 700 taken on line A-A of FIG.9. Protective cover 1006 is shown disposed over insulation 1004 which isaround foamed asphalt pipe 1002.

It is believed that when these teachings are combined with the knownprior art by a person skilled in the art of WMA asphalt drum design andoperation, many of the beneficial aspects and the precise approaches toachieve those benefits will become apparent.

It will be understood that certain features and sub-combinations are ofutility and may be employed without reference to other features andsub-combinations. This is contemplated by and is within the scope of theclaims.

Since many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

1. A method of making warm mix asphalt comprising the steps of: providing an asphalt plant rotating drum; providing an asphalt expander configured to accept heated asphalt cement (A/C) and generate an expanded asphalt foam; providing measured and controlled amounts of water to said asphalt expander; selectively providing measured amounts of A/C to a plurality of A/C delivery pipes; wherein said plurality of internal A/C delivery pipes comprises a hot mix asphalt cement internal drum delivery pipe and a warm mix expanded asphalt injection pipe assembly; providing an asphalt cement check valve between said asphalt expander and said and a source of measured amounts of asphalt cement; wherein said asphalt expander is free of any moving internal parts therein and comprises: an asphalt expander material input top end; asphalt expander material output bottom end; a longitudinal asphalt expander axis extending from a central location at said asphalt expander material input top end to a central location at said asphalt expander material output bottom end; a double side wall pipe extending from the top end to the bottom end, disposed coaxially about said longitudinal asphalt expander axis; asphalt expander interior central support shaft disposed along said longitudinal asphalt expander axis; an omni-directional flow diverter disposed on top of said support shaft and inside said material input top end; said omni-directional flow diverter configured to divert incoming heated A/C to only a plurality of peripheral locations inside said double sidewall pipe; a fluid injection ring disposed circumferentially around said longitudinal asphalt expander axis and configured to provide a ring of flowing fluid to contact the heated A/C at said plurality of peripheral locations; a plurality of expansion flow diverters disposed below said fluid injection ring configured to mix a flow of foam created as the ring of flowing fluid contacts the heated A/C being pumped into said asphalt expander; and said asphalt expander further having a plurality of ports for aiding in the flow of heated oil through a cylindrical void located coaxially about said longitudinal asphalt expander axis in said double side wall pipe.
 2. A method of providing warm mix asphalt, the method comprising the steps of: providing a rotating drum configured to receive at an aggregate receiving end aggregate material, and further configured to create hot mix asphalt with drum exit temperatures in excess of 275 degrees Fahrenheit; providing an asphalt expander configured to receive heated asphalt cement and mix in water at a rate of between 1% to 4% water weight to A/C weight, and thereby form an asphalt foam without contacting any moving parts within said asphalt expander; the asphalt foam being of a consistency to coat aggregate material at a lower aggregate material temperature; and distributing said asphalt foam within said rotating drum and contacting heated aggregate moving therethrough and thereby creating warm mix asphalt with a rotating drum exit temperature of between approximately 220 degrees to 275 degrees Fahrenheit.
 3. The method of claim 2 wherein said step of distributing said asphalt foam comprises, providing a single pipe which is configured to distribute both expanded foam and non-expanded asphalt cement and further comprising the steps of heating said asphalt foam while disposed in said asphalt expander.
 4. The method of claim 3 where said step of heating said foam further comprises the step of providing heated liquids to said asphalt expander.
 5. The method of claim 4 wherein said step of heating said asphalt foam further comprises, providing a void disposed about an exterior of said asphalt expander configured to receive therein and to pass therethrough heated liquids.
 6. The method of claim 5 further comprising a step of automatically controlling a rate of water provided to said asphalt expander, so that weight of said water is set to be at a predetermined point within a range of 1% to 4% of a weight characteristic of said A/C.
 7. The method of claim 5 wherein said water is substantially clean water, being free from material which would substantially affect production of asphalt foam upon mixture of said water with said A/C.
 8. The method of claim 7 which includes a step of creating a flowing curtain of clean water.
 9. The method of claim 8 further comprising a step of diverting a flow of A/C through said flowing curtain of clean water.
 10. The method of claim 9 further comprising the step of providing a plurality of diverters to increase homogeneity of foam created when said flow of A/C meets said flowing curtain of clean water.
 11. A method of creating warm mix asphalt, the method comprising the steps of: providing a rotating drum configured to receive at an aggregate receiving end aggregate material; providing an asphalt expander configured to receive heated A/C, mix therein clean water at a rate of between 1% to 4% water weight to A/C weight, and thereby form an asphalt foam without contacting any moving parts within said asphalt expander; and distributing said asphalt foam within said rotating drum and contacting heated aggregate moving therethrough and thereby creating warm mix asphalt with a drum exit temperature of between 220 and 275 degrees Fahrenheit.
 12. The method of claim 11 further comprising the steps of: providing a controlled amount of water to said asphalt expander and forming a curtain of flowing water inside said asphalt expander.
 13. The method of claim 12 further comprising the steps of: creating a moving ring of A/C which contacts said curtain of flowing water.
 14. The method of claim 13 wherein said step of distributing said asphalt foam comprises the step of providing a single pipe which is configured to distribute both asphalt foam and non-expanded asphalt cement and distributing said asphalt foam through said single pipe and further comprising heating the asphalt expander to transfer heat inside said asphalt expander after cooling has occurred after steam is given off when said ring of A/C contacts said curtain of flowing water; were said curtain of flowing water is a curtain of flowing clean water.
 15. An asphalt production method comprising the steps of: providing a counter-flow asphalt plant rotating drum; providing an asphalt expander configured to accept asphalt cement (A/C) and generate an expanded asphalt foam; providing measured and controlled amounts of water to said asphalt expander; selectively providing measured amounts of A/C to a plurality of internal drum A/C delivery pipes; wherein said plurality of internal A/C delivery pipes comprises a asphalt cement internal drum delivery pipe and a expanded asphalt injection pipe assembly; providing an asphalt cement check valve between said asphalt expander and said means for selectively providing measured amounts of asphalt cement; wherein said asphalt expander is free of any moving internal parts therein and comprises: an asphalt expander material input top end; asphalt expander material output bottom end; a longitudinal asphalt expander axis extending from a central location at said asphalt expander material input top end to a central location at said asphalt expander material output bottom end; a double side wall pipe extending from the top end to the bottom end, disposed coaxially about said longitudinal asphalt expander axis; asphalt expander interior central support shaft disposed along said longitudinal asphalt expander axis; an omni-directional flow diverter disposed on top of said support shaft and inside said material input top end; said omni-directional flow diverter configured to divert incoming A/C to only a plurality of peripheral locations inside said double sidewall pipe; providing a fluid injection ring disposed circumferentially around said longitudinal asphalt expander axis and configured to provide a ring of flowing fluid to contact the A/C at said plurality of peripheral locations; providing a plurality of expansion flow diverters disposed below said fluid injection ring configured to mix a flow of foam created as the ring of flowing fluid contacts the A/C being pumped into said asphalt expander; and said asphalt expander further having a plurality of ports for aiding in the flow of oil through a cylindrical void located coaxially about said longitudinal asphalt expander axis in said double side wall pipe.
 16. The method of claim 15 wherein said ring of flowing fluid is a water ring.
 17. The method of 16 wherein said water ring is a continuous curtain of flowing water.
 18. The method of claim 17 wherein said expanded asphalt injection pipe assembly comprises a plurality of nozzles configured to disperse a heated foam. 